One document matched: draft-froment-sipping-spit-requirements-00.txt
SIPPING H. Tschofenig, Ed.
Internet-Draft Nokia Siemens Networks
Intended status: Informational G. Dawirs
Expires: December 16, 2007 University of Namur
T. Froment
Alcatel-Lucent
D. Wing
Cisco
H. Schulzrinne
Columbia University
June 14, 2007
Requirements for Authorization Policies to tackle Spam for Internet
Telephony and Unwanted Traffic
draft-froment-sipping-spit-requirements-00.txt
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Internet-Draft SPIT Authorization Policy Requirements June 2007
Abstract
Spam over Internet Telephony (SPIT) is one of the foreseen future
forms of spamming that SIP open-wide networks may have to handle.
SPIT also has more impact on users than email spam since it is more
intrusive. Email as a store-and-forward communication mechanism
allows for several filtering mechanisms to be applied to the full
content before being presented to the user. Session Initiation
Protocol (SIP) interaction is, in contrast, real-time communication
and therefore does not provide much information prior to the
transmission of the content, making it both harder to filter and more
annoying to users. The responsibility for filtering, blocking calls,
or taking any other preventive action can belong to different
elements in the call flow and may depend on various factors.
This document discusses the requirements to define authorization
policies that should allow end users or other parties to setup anti-
SPIT policies for triggering these actions. These policies typically
match a particular SIP communication pattern based on a number of
attributes. The range of attributes includes information provided,
for example, by the SIP protocol itself, by the SIP identity
mechanism, by information carried within SAML assertions, reputation
systems of social networks and other extensions.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Conditions . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Actions . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Transformations . . . . . . . . . . . . . . . . . . . . . 8
3.4. Generic Requirements . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
7.2. References . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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1. Introduction
The problem of SPIT is an important challenge and it appears that a
combination of several techniques is desirable to provide a framework
to deal with it.
One important building block is to provide a mechanism to instruct a
trusted SIP proxy or any other SIP element to influence message
handling of incoming requests according to policies. Different
entities, such as end users, parents on behalf of their kids or
system administrators, might create and modify authorization
policies.
Some attributes in an incoming message play a more important role
than others. For example, applying authorization policies based on
the authenticated identity, see [RFC4474], is an effective way to
make decisions regarding unwanted traffic in many cases.
This document identifies requirements for authorization policies when
used to influence message handling for unwanted communicaion
attempts.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119],
with the important qualification that, unless otherwise stated, these
terms apply to the design of the authorization policies, not its
implementation or application.
The term 'Rule Maker' is defined in RFC 3693 [RFC3693].
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3. Requirements
This section lists the requirements categorized according to their
applicability for the "conditions", "actions" and "transformation"
parts of authorization policies. Furthermore, we describe
requirements that are more generic in nature and apply to the entire
rule set.
3.1. Conditions
The first set of requirements refer to identity related information.
Req-C 1: Policies MUST allow conditions to express single
authenticated identities.
Req-C 2: Policies MUST allow filtering based on the domain part of
the identity.
Req-C 3: Policies MUST support the differentiation between
authenticated and unauthenticated identities.
Req-C 4: Policies MUST be able to express expections within a group
of users/domain.
Message handling might be different depending on the content of the
SIP message header fields.
Req-C 5: Policies SHOULD allow conditions to refer to the
"destination" (which corresponds to the "Request-URI") and
"original-destination" (which corresponds to the "To" header).
Req-C 6: Policies SHOULD allow conditions to refer to the method
invoked by the caller (e.g., INVITE, REFER, MESSAGE).
Motivation: Some SIP methods are more intrusive than others
(the default applicative behaviour when SIP MESSAGEs are
received is often to pop-up the message on the UAS side),
adopting a different filtering policy depending of the method
invoked will enhance the user's protection.
Req-C 7: Policies SHOULD allow Rule Makers to take actions on
messages that are marked as Spam.
Note that such a condition element should be seen in
context of the authenticated domain or or otherwise
protected information to avoid security
vulnerabilities.
[Editor's Note: Should we allow message handling based on the
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existence or non-existence of certain SDP / SIP content, such as
specific mime types? For example, is a "exists" test useful that
returns true if the headers listed in the argument exist within the
message. Furthermore, do we need test operators (such as "allof" and
"anyof", which implement logical "and" and logical "or",
respectively)?
Message handling might be different based on time.
Req-C 7: Policies SHOULD allow conditions that refer to the
reception date, time or period of time of the incoming
request.
Message handling might be different based on the language.
Req-C 8: Policies SHOULD allow to make decisions based on the
languages in which the originator of the call wishes to
communicate.
Message handling might be different based on the SIP resource
priority fields, on emergency service related messages or more
generic forms of indicating the type of service.
Req-C 9: Policies MAY allow to make decisions based on the presence
of SIP Resouce Priority headers, as described in [RFC4412].
Req-C 10: Policies SHOULD allow to make decisions based on the
messages marked as emergency calls indicated in
[I-D.ietf-ecrit-service-urn].
Req-C 11: Policies MAY allow to make decisions based on service
identification fields, see
[I-D.rosenberg-sipping-service-identification].
3.2. Actions
Req-A 1: Policies SHOULD allow messages to get "blocked", i.e., to
stop forwarding the request and to return an answer with a
``403 Forbidden''
Req-A 2: Policies SHOULD allow messages to get "politely blocked",
i.e., to drop the request without returning an answer.
Req-A 2: Policies SHOULD allow messages to get "marked", i.e., to
forward the request and mark it as "potential Spam" for
filtering at the end point or at subsequent entities along the
signaling path.
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Req-A 3: Policies SHOULD allow messages to be "allowed", i.e., to
forward this message.
Req-A 4: Policies MUST allow messages to be "redirected" to, for
example, voicemail or to a different device in the possession
of the user.
Req-A 5: Policies MUST allow the ability to execute other SPIT
prevention procedures, such as computational puzzles
[I-D.jennings-sip-hashcash] or the consent framework"
[I-D.ietf-sip-consent-framework]. Ideally, a specification
developing a SPIT prevention mechanism SHOULD provide
information on how they can be incorporated into the
authorization policy framework.
As an example, for a statistical analysis tool a URI is
defined. The algorithms itself do not need to be
standardized and hence the impact for authorization
policies is mainly the ability to allow a Rule Maker to
enable or to disable the usage of these statistical
techniques for SPIT filtering and potentially to map
the output of the analysis process to value range from
0 (i.e., the message is not classified as Spam) and 100
(i.e., the message was classified as as Spam). A Rule
Maker may decide the appropriate action on the message
depending on the determined SPIT probability.
Req-A 6: Policies MAY allow an e-mail (or SMS, MMS) to be sent to
the user about the actions taken due to a specific call
attempt.
3.3. Transformations
Req-T 1: Policies SHOULD allow SIP messages to be marked with a
certain SPIT probability in case SPIT detection and policy
enforcement is excecuted on different entities. For example,
a network element might run a statistical SPIT detection tool
but the authorization policies are executed on a different
entity, such as the end host. Note that it needs to be
ensured that an adversary is not able to set the SPIT
probabity values since otherwise the authorization policies
that rely on such information are misguided.
3.4. Generic Requirements
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Req-G 1: It SHOULD be possible to allow a hierarchy of authorization
policies to be used.
Req-G 2: It MUST be possible for a client to learn the supported
authorization policy capabilities implemented by the server.
Req-G 3: Policies MUST be extensible and these extensions MUST exist
within a different namespace. Furthermore, a published schema
and the namespace for elements defined within it MUST NOT be
altered by future specifications.
Req-G 4: The policies MUST provide a mandatory-to-implement conflict
resolution mechanism.
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4. IANA Considerations
This document does not require actions by IANA.
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5. Security Considerations
This document describes the requirements for elements contained in
the authorization policies that allow communication attempts to be
treated differently based on the content of the message, time-of-day,
context of the user, reputation of the sending party, and many other
factors.
The security concerns are related to the ability of certain entities
to create, update and delete authorization policies. If an
unauthorized entity is allowed to modify policies (and to distribute
them to other domains) then a denial of service attack is the
consequence with impact for more than a single end point. These
security aspects are, however, not subject of this document.
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6. Acknowledgements
The content of this document is inspired by the work of CPL
[RFC3880], SIEVE [I-D.ietf-sieve-3028bis], Common Policy [RFC4745]
and Presence Authorization Policy [I-D.ietf-simple-presence-rules].
We would like to thank the authors of these documents for their work.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. References
[I-D.ietf-ecrit-service-urn]
Schulzrinne, H., "A Uniform Resource Name (URN) for
Services", draft-ietf-ecrit-service-urn-06 (work in
progress), March 2007.
[I-D.ietf-sieve-3028bis]
Showalter, T. and P. Guenther, "Sieve: An Email Filtering
Language", draft-ietf-sieve-3028bis-12 (work in progress),
February 2007.
[I-D.ietf-simple-presence-rules]
Rosenberg, J., "Presence Authorization Rules",
draft-ietf-simple-presence-rules-09 (work in progress),
March 2007.
[I-D.ietf-sip-consent-framework]
Rosenberg, J., "A Framework for Consent-Based
Communications in the Session Initiation Protocol (SIP)",
draft-ietf-sip-consent-framework-01 (work in progress),
November 2006.
[I-D.jennings-sip-hashcash]
Jennings, C., "Computational Puzzles for SPAM Reduction in
SIP", draft-jennings-sip-hashcash-05 (work in progress),
June 2007.
[I-D.rosenberg-sipping-service-identification]
Rosenberg, J., "Identification of Communications Services
in the Session Initiation Protocol (SIP)",
draft-rosenberg-sipping-service-identification-02 (work in
progress), May 2007.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3880] Lennox, J., Wu, X., and H. Schulzrinne, "Call Processing
Language (CPL): A Language for User Control of Internet
Telephony Services", RFC 3880, October 2004.
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[RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Priority for the Session Initiation Protocol (SIP)",
RFC 4412, February 2006.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
Polk, J., and J. Rosenberg, "Common Policy: A Document
Format for Expressing Privacy Preferences", RFC 4745,
February 2007.
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Authors' Addresses
Hannes Tschofenig (editor)
Nokia Siemens Networks
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Email: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.com
Geoffrey Dawirs
University of Namur
21, rue Grandgagnage
Namur B-5000
Belgique
Email: gdawirs@gdawirs.be
Thomas Froment
Alcatel-Lucent
Route de Villejust
Nozay, Paris 91620
France
Email: Thomas.Froment@alcatel-lucent.fr
Dan Wing
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: dwing@cisco.com
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Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs@cs.columbia.edu
URI: http://www.cs.columbia.edu
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